What’s the (Dark) Matter?
John at 7:43 pm, February 27th, 2008There really is something out there, bending the light from distant galaxies:
Galaxies, and galaxy clusters, appear to be surrounded by clouds of something invisible which interacts gravitationally. It apparently also causes the rotation of galaxies to deviate from the simple prediction of Newton’s laws assuming that only the visible matter in galaxies is present.
This “dark matter” makes up nearly a quarter of the mass/energy density of the universe, whereas “light matter” (stars, interstellar dust and atoms) make up only a few percent.
Our prejudice is that dark matter has a particle nature. Theories of particle physics beyond the Standard Model these days offer many possibilities for dark matter candidate particles, many of which could be detected via their weak interactions with ordinary matter. Here we mean weak in the sense of interacting by exchanging a W or Z boson with the ordinary matter particles. The common thread among the particles proposed for dark matter is that they are weakly interacting and massive (of the order of hundreds of times the proton mass - one to several hundred GeV). Particles in this general class of dark matter candidates are called WIMPs.
If WIMPs are really there, there are only a few per cubic meter in our galaxy, and most fly straight through ordinary matter without interacting. But, if they can and do interact weakly, occaisionally they could transfer enough energy to a nucleus of ordinary matter that it would be detected, if our equipment is sensitive enough. Also, there is hope that WIMP dark matter particles could be created in the high energy collisions of the Tevatron at Fermilab or soon at the LHC at CERN, and detected indirectly by the fact that they carry away apparently missing energy.
Experimentally, now, in the area of direct detection there is a race on between two main competing technologies for observing the feeble signal of WIMP interactions. Until a few days ago, the most sensitive search for WIMPs was that of the XENON10 collaboration, using a detector of liquid and gaseous xenon as the target for the WIMPs. The detector is kept deep underground at the Gran Sasso Laboratory in Italy. But at the Dark Matter 08 meeting in Marina del Rey last week, the lead in this search was recaptured by the Cryogenic Dark Matter Search collaboration. They use solid crystalline silicon and germanium detectors, cooled to liquid helium temperatures, to sense the nuclear recoil from WIMP interactions, taking extraordinary measures (as all these experiments do) to avoid false signals from cosmic rays, natural radioactivity, and stray neutrons. They did a blind search, making carefully controlled predictions of the number of WIMP signal events they expected to see, and then “opened the box” earlier this month. They expected 0.6 background events, give or take about half an event. The result: nothing. No signal from WIMPs or backgorund or anything!
To “measure nothing” is usually a great experimental challenge. You do have to convince the world that you would have seen something if it had been there, that your apparatus isn’t just mute for some other reason. CDMS have done a great job convincing the world of this, I’d say, and their result is nearly a factor of three more constraining than the previous Xenon 10 result. They show it in this plot of WIMP interaction strength versus WIMP mass:
What the plot is saying is that assuming that all dark matter is a WIMP of a certain mass, there is less than a 10% chance that, if the spin-independent cross section had some value greater than that indicated by the heavy black line, they would have seen no events in the detector. This can be turned around to say that at the 90% confidence level if such WIMPs exist, they must have even feebler interaction strengths than that indicated by the heavy black line.
These exclusion limits are starting to cut deep into the theoretically favored regions indicated on the plot…and the fact that there really are zero events at this stage means that any sort of five sigma discovery could be a long way away.
In the mean time, there are larger xenon based experiments planned, including a larger version of the Gran Sasso one and the LUX experiment, to be based at the nascent deep underground facility DUSEL.
And, perhaps as early as later this year, the LHC experiments CMS and ATLAS will begin to get a glimpse of the results of protons “colliding in anger” as a colleague of mine likes to put it. The Tevatron has seen no hint of WIMP production/decay yet, and so with seven times more energy, the LHC maybe able to produce the heavy particles that decay down to lighter ones which may include WIMPs such as the neutralinos predicted by supersymmetry.
I muse from time to time on the possibility that dark matter may really only interact with “light matter” gravitationally. Perhaps it is composed of an entirely separate sector which does not interact with light matter. It may be several or many particles which interact amongst themselves, forming structures we can only speculate about. If our only probe of dark matter is gravity, there will be a very long road ahead to understand it. I hope the cosmologists among the readers here can offer us more hope that indeed, there are strong reasons to believe dark matter interacts weakly…
You expect dark matter to be produced in the early universe and can relate its observed abundances to the scale of its interactions which is why one expects a weak scale interaction with visible matter. I don’t know what the bounds are on dark matters self-interaction, however, but I’m sure someone reading this does….
“Our prejudice is that Dark Matter has a particle nature”….
Well spoken, Sean…good word choice too!
I’m sorry, I’m still convinced that “dark matter” is what scientists have made up to help all their sums add up correctly.
Well spoken, Sean…good word choice too!
Sean didn’t write that — John did.
Elayne…adding up sums is one thing. But how do you explain the lensing photo? There simply is not enough ordinary matter to bend the light that much…by a factor of six!
Thanks, John. A basic question:
“Here we mean weak in the sense of interacting by exchanging a W or Z boson with the ordinary matter particles.”
Is this the same sort of interaction that neutrinos have with protons/neutrons?
Also, when you say there was no background, does that mean that nothing at all was detected by the detectors, or that the observed detector response matched the predictions for electronic noise/background radiation/etc?
Hi John - thanks for the publicity for our result!
As the maker of this plot, I should note that the confidence levels are 90% rather than 95%.
In answer to Lab Lemming’s second question, we did observe many thousands of events in our detectors - we’re quite sure they’re working. We developed a series of “cuts” on the data, defining a region of parameter space in which we expect dark matter signals to lie but background events to avoid. These cuts were developed “blindly” - we didn’t know exactly where all of the events were when we set the cuts, so we couldn’t “force” the answer to be zero or any other number. When all the cuts were applied, no events were seen. This was consistent with our expectations from our understanding of the events in our detectors and the performance of our cuts.
Thanks Jeff, I changed 5%/95% to 10%/90%. We all do 95% CL in the collider physics world…
Direct detection dark matter experiments are finally probing SUSY theoretical estimates, and these are indeed exciting times for both theorists and experimentalists. Even though CDMS-II just recently “recaptured” the title of most sensitive in the world, the XENON10 (which, by the way John, *must* be capitalized - people in the collaboration like it that way) experiment was a mere prototype of double-phase noble liquid detection mechanisms, and it made a strong case against cryogenic technologies, which will not be able to keep up with tonne-scale xenon/argon detectors in the next decade.
I happen to work on the LUX experiment, and I’m quite excited for this next-generation dark matter detector to probe unexplored regions of the WIMP’s parameter space. XENON100, XMASS and WARP (if they figure out how to get rid of Ar39) should also yield interesting results in the next couple of years.
btw, I believe the spin-independent plot you’re showing needs some reference (it’s from Richard Gaitskell, Mandic and Filippini)
I’m no scientist but I agree with Mr. Cox. Why does dark matter have to be matter at all? If it only presents itself as a gravitational manifestation pushing galaxies apart at ever increasing speeds then maybe it IS gravity or the opposite of gravity “leaking” out of the other dimensions string theorist are so adament about.
charly:
I am exceedingly impressed by the performance of the noble liquid prototypes, and I’m also excited by the prospects of LUX, WARP and the rest. There’s still a lot to be proved for all of us in terms of background rejection, of course, but the prospects are good. Cryogenics should not be counted out just yet, however!
Rick Romano:
There are theories of dark matter of this ilk, but my impression is that it’s generally hard to make them agree with the whole range of current observations.
John, great post. Although (despite getting mistaken credit for it above) I wouldn’t quite say that it’s a prejudice that dark matter is particles. It acts like it’s made of particles, in particular non-relativistic one. From what we know, it clumps and distributes itself just like a massive non-interacting particle would. (And, say, cosmic strings or a smooth potential field would not.) Not a proof, obviously, but a bit more than a prejudice.
We should distinguish between the technical term “weakly interacting massive particle” and “particles that don’t interact very much” — the DM is the latter, and possibly the former (in which “weak” means “the weak nuclear force”), but not necessarily. Axions are a standard example — they don’t feel the weak force, which is consistent with what Aaron says above because they were never in thermal equilibrium in the early universe.
There certainly may be DM particles that have no more than gravitational strength interactions with ordinary matter; Wimpzillas are an example. An overview of limits on self-interactions for DM is here.
It’s okay to contemplate the possibility that there is no DM, just modified gravity, but the data are running strongly against that idea.
Mark had a nice post about the theoretical side of these issues.
Ah, the naming of particles. Wimpzilla sounds to me like the least scary sci-fi monster ever. As I’m only interested in physics, but not an initiate, that’s all I can add to the discussion, I’m afraid.
If the only interaction between normal matter and dark matter was gravity, though, how would it have ever been produced? It seems to me that the fact that it exists at all is an indication that dark matter and normal matter must interact at some level. I guess it’s just a question of how high in energy you have to go.
FYI, a .png or .gif would be a better format choice for plots. .jpg ’s are a lossy compression format designed for photographs. With many computer generated content, like plots or text, .jpg ’s are hard to read.
It is also instructive to realise that most of the “light matter” is in fact dark!
The visible matter in the universe comprises of ~0.2% stars, ~0.1% nebulae, whereas the baryonic component of the universe is ~4%. (Percentages of the critical density)
The baryonic percentage is constrained by the standard Big Bang Nucleosynthesis (BBN) model, which more of less fits the observed element relative abundance, but which is sensitive to the expansion rate of the early universe.
There is about 13 times the amount of baryonic matter in unseen components as in visible components. This may be in the forms of Warm Hot Intergalactic Medium (WHIM) , Intermediate Mass Black Holes (IMBHs) , inter-cluster atomic hydrogen and the like.
Could it be that some form of DE acted during the nucleosynthesis stage thus slowing down cosmological deceleration and prolonging the BBN epoch thus increasing the baryonic component of the universe? In this scenario all DM may be baryonic in form and invisible in the same way that the majority of baryonic matter in invisible in the standard model.
The problem with this hypothesis is of course is that of finding concordance with other cosmological constraints – and finding all that conjectured the ‘missing matter’!
Garth
Rick,
That would be dark energy. Dark matter is gravitational effect with no apparent source. It might be that the source is invisible, or it might be a problem with the model.
If dark energy is something “leaking” out of other dimensions and consequently falling into gravitational wells, then expanding space wouldn’t be a BB event, but a process, one side of a convective cycle. So the age of the universe isn’t limited and galaxies are far older then currently assumed, so they might have had the time to overcome all drag and pull the outer bands up to speed with the inner ones. Especially since this “expansion” would also create external pressure on galaxy systems. This warping of space by expansion/gravitational contraction would bend light a fair amount. Just an idea.
Now that was a post worthy of a scientist. Good use of conditional language - ‘apparently’, ‘prejudice’. Informative. Totally devoid of name-calling and snarky comments.
Thanks, John - it’s a lot to absorb for a non-physicist, but I’m working on it.
I don’t mean to add this to such a great physical discussion, but isn’t this invoking the exact argument of the paranormal post a week ago? It is simply that we are seeing a mass scale form of “weakly interacting” force particles. Perhaps if we had mass scale psychics… hehe, joking… kind of. Just a note.
For relevant information, this is an article that made an impression. I am aware that data pushes for actual particles (force particles? is this possible or would that be incorrect?), but the idea of a model that, after given the proper time or attention for construction (which there clearly hasn’t been enough of either), may fit data at some point in the near future?
Also, I enjoyed Garth’s post thoroughly. I feel that argument fits so much more simply. It could be possible our cosmological horizon hides the remains of interacting matter that simply isn’t visible as space is warped at this horizon. Imagine this, two ‘dots’ on opposite sides of a piece of paper normally unable to interact gravitationally, with us at one of the dots. Then, some mass at the horizon is so great that it folds the paper, or the dimension of space, and the dots can then interact because the space between them, through the higher dimension, is reduced through the folding of the lower dimension.
[Imagining the Tenth Dimension]
The DM we observe as adding to the gravitation of these galactic observations, may simply be matter on the other side of that fold interacting through the higher dimension, with the matter we observe. No DM, straight baryonic.
May be a bit for most to wrap (or fold, hehe) their minds around, but I would consider it legitimate. Especially since our current model of the big bang assumes that at our horizon (that we cannot yet see) the mass of the universe is ‘very large’ (I won’t use ‘infinite’ here), as this would be the ‘beginning of time and space.’ If all matter is conjoined at this one point, the beginning of expansion, then of course at that point there is some form of dimensional warping because of its high density. Matter warps space. Absolute observable matter at one point, warps all observable space at one point absolutely.
Perhaps I overextended myself, but I hope this doesn’t deter the argument at hand.
I feel that a lack of creativity in the world has led to arguments of a mysterious nature. We require leaps of consciousness to find answers, rather than leaps of ‘faith’ in dark matter/energy. Be careful not to become as faithful as the religions you so heavily deride, scientists and physicists. For this is what you call the schmoe on the street to do in this case, in this 96% darkness, these WIMPS. Can’t see it, can’t touch it, we must have faith in it? Preposterous.
Wayne
The WIMP density is inversely proportional to the annihilation cross section, which in turn should be of the same order as the WIMP- Nucleon cross section. One of the reasons why WIMPS are a favored DM candidate is because weakly interacting particles have cross sections that are consistent with the known DM density.
However, as the cross sections are constrained to be lower and lower by direct detection experiments, they’ll soon lose their “most favored status”
The new dark matter sensitivity limit reached by CDMS is quite extraordinary indeed. I have to agree with Charly (my lab mate in fact, we both work on LUX) that currently the most scalable technology is that of the noble liquid detectors (tonne scale talk is getting quite prevalent). Of course, this new result does in fact show that Si, Ge detectors are still worthwhile. In fact, for dark matter to be considered ‘detected’ it needs to be found by several experiments and even several different technologies (direct and/or indirect). This is, of course, the nature of experimental science.
Once again, congratulations to the CDMS collaboration!
John or Sean, what is the latest status of the
DAMA claim for detection of Dark matter. I thought they were building a bigger detector for it.
Sean , besides the bullet cluster, another pristine test (besides of course
direct detection or production of dark matter) of the existence or non-existence
of dark matter would be through grav. wave observations.
Re DAMA, there is a new paper out by the COUPP collaboration that effectively rules out the remaining DAMA region ( putting new limits on “spin-dependent” interactions)
See COUPP Results
which contains links to the press release and paper.
Ask and ye shall receive. My thanks, and compliments, John–it couldn’t have been better. I also note that the excellence of your post is echoed in the clarity of the comments.
Sorry, Count, could you provide a brief explanation or link for those of us not as versed, for what you mean by cross-sections and annihilations, etc?
The new DAMA/LIBRA results will be announced at the end of this year. The only thing that has been “ruled out” is that the DAMA signal could be due to WIMPS. Although the DAMA team will dispute this for the spin dependent case, because for spin dependent interactions it is more difficult to compare different results from different detectors.
There are many other ways one can account for both the null results of CDMS and the positive DAMA results (just search the arXiv for DAMA), so it would be wrong to say that just because other searches didn’t find anything, the DAMA results must be due to experimental error.
Wayne, I have to go now, but very briefly, lower sigma means that in the early universe WIMPS decouple earlier As the universe expands the density becomes lower so interaction proability will become lower as a function of time. At a certain point the WIMPS don’t interact at all, but that will happen sooner the lower the cross section is. This means that the lower the cross section the higher the temperature of the WIMPS at the point they decouple. This leads to a higher final WIMP density.
Dark matter appears to be what I would call cosmic cobwebs. The stuff appears to form strings and tendrils which connect galaxies and galactic clusters. Dark matter astronomically appears to interact with itself, or that it has fluid-like properties very different from a gas. This would suggest that DM is different from a standard particle with a mass.
I frankly think it is related in some ways to a vacuum state. Maybe if dark energy is a vacuum state with w = -1, then dark energy is some alternate state, similar to gas bubbles in ice, embedded in a overall cosmic vacuum state which might be some sort of quantum critical point analogous to what occurs with Landau liquids of electrons and the so called breakdown of the fluid at the critical point with quasiparticles.
It does not surprise me that WIMPS were not found, and I have reasons to think that SUSY pairs are not particles in the standard sense. Maybe the LHC will produce SUSY pair particle. Yet I think that the SUSY pairs in E_8xE_8 are associated with an intersection form for gravitational instantons.
Lawrence B. Crowell
Thanks Aaron…John’s name is tucked way up there!….at any rate…
Again a great thread, with many interesting reflections on DM. Waynes’ comments on dimensional effects was interesting. A 4D framework can only accomodate macroscopic dimensions a millimeter or so in size, but I don’t see why we need to look (curiosity perhaps) for additional dimensions in an observed universe which is already known to be defined by only 4.
Higher dimensions may be huge, vast, whatever. As Wayne points out, they are just not found in the ways they are presently being searched for. Addtional mass in the universe is a great clue to the possibility of extra large dimensions. So is the mathematical determinism implicit in SR/GR and QM…for starters.
I’m not sure of the relevance of the scientist Nigel Cook’s article here
http://nige.wordpress.com/2008/01/30/book/
where among other things he states what he believes is the “correct model of quantum gravity…gravitons are
spin-1 gauge bosons, not spin-2.”
He acknowledges that his thinking is outside the mainstream. I just wonder how far outside, or is he on to something?
Well Sam, to us, can’t we very well be within a 3D space that is the size of a millimeter? We’d never know, would we? Physics doesn’t break down if we simply change the order of magnitude we consider our universe to be occupying. It’s a matter of perspective in my opinion.
Here’s another article that shows how even accelerated expansion attributed to DE may be false.
http://www.physorg.com/news123429057.html
Enjoy, good hunting fellas.
Wayne
If the rotation of galaxies is dominated by dark matter, how far from the sun would a spacecraft have to get before the dark matter gravitational field started to dominate that of the sun?
So MOND is kaput for sure, since we have enough data on DM distribution? (That’s the key, variations in density versus a general tweak to gravitational attraction.) I’d heard though, MOND was the only way to deal with Pioneer 10 anomaly. But could distributions of DM have to do with that also? MOND was theoretically interesting because the tiny acceleration regime below which attraction was non-linear, happened to be given by c divided by the lifetime of the universe (then it would have to change.) REM also the concept of “shadow matter” which is not quite the same idea (the form of stuff which only interacts gravitationally with ordinary matter.) DM may be SM however, presumably.
One more small note on this posting: the CDMS detectors are actually cooled to about 40 milliKelvin, about 100x colder than liquid helium temperatures.
MOND is really nothing more than phenomenology. You could modify gravity perfectly to account for the gravitational rotation of the galaxy by dark matter. MOND is to my mind almost a gravitational “form factor” of sorts.
MOND as a new fundamental theory of gravity is not likely.
Lawrence B. Crowell
Wayne,
There are key proportions, mass and energy limits involved in the observed universe, which when replicated, would produce somethng on the order of “size” that we observe. I can tell by your use of “3-Space” that you know that what is commonly- and pretty loosely- referred to as “the 5th dimension” is really the result of adding an additional 3-space to the geometry of the universe. Such an antimatter based particulate reality, would not be measurable, space wise because it would be completely “over the horizon” in a Schwarzschild two-sphere, “mirror” (actually quite chiral, with quite different physics) other unseen side of the universe. The mass WOULD be detectable though, from our frame of reference. Its also interesting that we live in a universe of random events, though the models which describe reality most accurately, are at their conceptual hearts, deterministic in the extreme. quantum fluctuations in the Planck Realm are random, but in the model we are presently using, overall, half the fluctuations would be expected to occur in one three space and half in the other…the basis for duality, which happens to also be mathematically implicit in our models!
Lab,
Good thought. Testable theories emerge by extrapolating from such conceptual ideas. The answer, by the way, is a long way. John used the word “prejudice” in sizing up the present search for dark matter as particles. In fact, being invisible, it is quite obvious that either dimensional horizons (as Wayne mentioned) are involved, or that dark matter may indeed just be another form of dark energy…an interesting subject. Quite a few scientists just speak of a universe made up of 96% dark energy…
“One more small note on this posting: the CDMS detectors are actually cooled to about 40 milliKelvin, about 100x colder than liquid helium temperatures.”
Isn’t the final cryogenic stage of CDMS a dilution fridge? That’s still liquid helium, although two different isotopes and the awesome power of the entropy of mixing are involved.
Sam, got an order of magnitude there? Are we talking 1000 au or 10,000? Or light years? If we can find some oort cloud objects, would it effect their orbital dynamics within observational error?
Tom #38:
Touche - that’s completely right. It is a dilution fridge so it’s cooled by liquid helium, just unusually cold liquid helium.
Lab Lemming,
The question is not quite well posed as is. The sun orbits the galactic center. Anything going around the sun is also revolving around the galactic center. Just like Earth’s moon goes around the Sun as well as the Earth. The question could ask, at what radius does an object no longer orbit primarily the Sun, but orbit the galactic center independently of the Sun? That is essentially the outer limit of the Oort cloud by definition - the Hill sphere (http://en.wikipedia.org/wiki/Hill_sphere) of the Sun. Outside that radius, the tidal field of the galaxy’s mass unbinds an object from the Sun.
I haven’t mentioned dark matter yet. The outer radius of the Sun’s influence is set by the Galactic mass distribution, and in the solar neighborhood, that’s mostly due to ordinary matter: stars, a bit of gas, old copies of the Astrophysical Journal. To get to a radius where dark matter dominates over the baryonic matter contribution to the rotation curve, you have to go out to perhaps 15-20 kpc - the exact number is hard to measure, especially in our own galaxy since we’re inside it.
Thanks for the tip, Ben.
I was under the mistaken impression that the speed of rotation out here in the arms was dominated by dark matter, not light.
I’ll go back to earth rocks, now that I’ve failed to con you cosmologist types into funding an outer solar system space probe for me, on which it would have been foolish not to include instrumentation for monitoring Io’s volcanoes during the mandatory Jupiter gravity assist.
I have made this comment here before, but it is worth making it again.
The “dark matter” hypothesis makes successful *predictions* — the form of the fluctuations in the microwave background would be radically different if the universe did not contain dark matter: the “acoustic peaks” rely on the presence of dark matter in the early universe. This prediction was made before the acoustic peaks were observed, and the theoretical calculations and observations match with astonishing precision.
Not only that, attempts to modify gravity in ways that explain either lensing or galactic dynamics without relying on dark matter typically cannot account for the observed form of the microwave background.
So there we have it: several different theoretical proposals, one of which (dark matter) makes successful predictions and several others which don’t.
There are certainly open questions about dark matter, but it is not simply a “fudge factor”, given that the dark matter hypothesis makes verifiable and tested predictions. (And from a particle physics perspective, we have very good reason to believe we have not observed all the particles that exist in nature, so it is not a radical suggestion to propose that there is some heavy particle that has not yet been seen accelerators.)
http://pda.physorg.com/lofi-news-dark-matter-energy_120998817.html
That is an article about what you were talking about Sam, in response to Lemming’s question. Dark Fluid. Spooky.
Thanks for clarifying the “mirror” (chiral) duality phenomenon. I see more of what you mean. Still the question arises that these two 3-Spaces would need to be embedded in a higher dimension to be detected at all? What I mean is, this still implies we wouldn’t just experiencing 3D space embedded in 4D time, but an intermediary “space” known as 5D through which we can detect our complementary, anti particulate neighbor. Also, the detectable mass should be able to interact with mass from our “side” too, right? How different is the physics involved on the other “side?”
So the 3D we experience could potentially be folded in such a way (not necessarily a sphere) that both the matter and antimatter realities could be quite close, able to be detected and interacted with, but still not be touching, maintaining the appearance of the “horizon.”
I feel like I’m throwing down a concept or two I might not be using correctly, but I would like to know what the proper usage is, if incorrect, to contribute more soundly in the future.
Thanks.
Wayne
http://www.physorg.com/news290.html
And one last one on the DF.
Wayne
Wayne,
You have the idea very well. The physics on each “side” would be different, but would completely make sense to particulate observers occupying a given 3-space. Remember in GR gravity, for example is a fictitious force…an acceleration resulting from the resistance of mass to peridic motion. Your link about acceleration outward by the way, is one of a number which questions whether the universe is actually accelerating outward in space and time. The Doppler effect is well understood, but many point out that gravitational time dilation on an antipodal (astronomical, big bang) event horizon as remotely observed would be expected to be extremely red-shifted, time and space (as remotely observed in that location) being tranformed and reduced. No actual motion need take place…the redshift is gravitational. This static interpretation is reasonable, and consistent with the way a GR universe would be expected to be observed.
Richard,
Well stated. The presence of that initial, very low acoustic peak is very interesting, as is the size of the second, which has led to our understanding that baryonic matter comprises not 2% but 4% of the universal mass.
Particles are energy according to the great proportion, so perturbations in the power spectrum could be caused by almost any kind of set of energy concentrations. I think what John is pointing out by using the word “prejudice” is that vast numbers of stellar sized black holes, observed from a distance in galactic arms could have the same effect overall, as particles. As you know, efforts to this point to detect these DM “particles” have been unsuccesful. What makes the situation even more mystifying is the invisibility of DM….
Sam, outstanding website. I thoroughly dig it. It complements every spiritual and physical concept that I’ve pursued in the years of my life, and offers an elegant explanation for the physical side of the cosmos. A healthy argument for the physicists at heart.
I’ve always viewed Einstein’s conclusions as deeply significant because of how intuitive they were, the ways they seamlessly melded the spiritual and the physical interpretations of experience and existence.
Thank you for the site. Fantastic. Thank you also for the discussion.
I suppose what remains after one follows their path in the cosmos towards reaching their personal understanding of such an intuitive concept, is to share their contentment, peace, and understanding with others by example; leaving their seeds wherever they fall, smiling inwards and outwards at the grand majesty of it all.
It’s never been a matter of one’s right or one’s wrong, but how we all get to the same place in the end, how worth it, how colorful, how gorgeous the experience of the path has been, and how blissful it feels to know we are entirely here, entirely there, that we could never be destroyed, never created– but ever reshaped, reformed, and reconnected by each other into the beauty we inhabit as creatures of the cosmos, here to experience this glory, love, wonder, happiness, awe… No God, no science, no law, no chaos. We only ever are, and only ever could be exactly what we need to be, where we need to be, at exactly the right time.
The spirit is for the spiritual, the physical for the physicist, but in either pursuit, as emphatic as each can be, will always hold the same answer. At the moment every one feels this brilliant intuition, and not a single moment before, will all be through and end, when we all start over and begin again.
Stay well Sam, good hunting to the rest,
Dearly,
Wayne
I don’t want to get ensnared in the lovefest between Sam and Wayne, but it is interesting to see what happens if you examine the suggestion that all the dark matter in the universe is in the form of stellar mass black holes. This certainly works in the sense that they are dark, and they are matter.
However, you then have to explain how they *formed* — and to explain the acoustic peaks in the CMB you need to have these black holes in existence when the universe was much younger than 300,000 years old. But you have to do that without making any big stars (whose radiation would stave off the recombination of the electrons and protons into hydrogen, and dramatically distort the CMB) at a redshift of 1000 or so, or other collapsed structures.
And then you have to explain where these black holes are today — since this many black holes in the galaxy would lead to far more microlensing events than we observe.
Hmmm.
And you would have to do all this without messing up nucleosynthesis — which, oddly enough, wants a baryon to photon ratio very similar to what we observe in the CMB.
So I can come up three or four objections to this idea while eating my lunch. In many ways cosmology is like whack-a-mole — solving any one problem is easy, but solving it in ways which do not make three or four new problems is hard.
Lawrence B. Crowell : “MOND is really nothing more than phenomenology. You could modify gravity perfectly to account for the gravitational rotation of the galaxy by dark matter.” Sure, in typical cases, but the important thing is that dark matter has its own distinguishing results, especially if not uniform all over (and it wouldn’t be.)
Richard,
How much of the current Standard Model would you consider falls in the category of easy solutions that only create more problems?
For example, one of the issues I’ve raised about the assumption that redshift is due to recessional velocity caused by expanding space is that the speed of light remains constant, so it would seem this would be increased distance in stable space, not expanding space. Which would put us at the center of the universe.
Dark matter is not composed of black holes, for as you point out there are not enough microlensing events. Yet I would presume that what ever composes dark matter, even if it is a vacuum state of one sort or the other, that this mass energy does enter into black holes. So this raises the question of whether there might be stronger microlensing events in regions of dark matter, such as galactic halos or the tendrils which connect galaxies.
A black hole might grow quite nicely and quietly in a region of dark matter. The black hole could absorb mass-energy without frictional heating and resistive effects of luminous matter which pushes most matter away from the black hole. Contrary to popular thought it is a bit hard to get a particle to enter a black hole. It has to come in pretty much dead on in a near perfect radial impact. A black hole immersed in a local “sea” of dark matter might find this to be an optimal zone of spacetime in which to “feed” and grow.
Lawrence B. Crowell
Wayne,
Thanks, and I really am awestruck by the universe, but it also has this nasty feral quality about it. Sailors have told me that the sea “waits”. If the unwary want to survive, they had better reproduce in vast numbers, quickly! As observing beings, we feel like we are forever on a tightrope, making critical decisions which must be informed if our existence is to continue…or maybe better, extended. Even if the universe is cosmologically deterministic, we have to assume there is some kind of phylogenically developing observational, informational complexity struggle going on against chaos, cosmologically, and that the uncertainty of events we observe at our frame of reference have roots somewhere in cosmological reality.
Richard,
Interesting points. It isn’t however, hard to understand why most of the universe is and must be singular. It is easy to drift to the geometric point conceptualization of the big bang and not carefully consider the fact that all frames of reference (information) in the GR system remains eternally at the same coordinates…that it is the collapse of space and time which causes everything to “be together” in a single low-entropy object. The standard model places constraints on the manner in which the universe developed and I agree this also places limitations on the role of black holes in this developing process of stellar and galactic formation. Without further be-laboring this, it is also pretty obvious that early stars were generally large and unstable, and that black hole development is a by-product of such instability. I’m willing to venture that scientists, at this point are very much underestimating the proportion of stellar sized black holes to “normal” stellar sequences and populations found in the universe.
LC,
To continue from that last sentence, black holes may not be dark matter, but your other comments are very appropriate, implying the presence of certain possible mechanisms for the the develpment of large amounts of invisible and pervasive”dark matter”. Mond is truly an interesting but incorrect concept. The jury is still out on WIMPS…
A thought occurred to me about dark matter. It must have a temperature. Some measurements last year I think did bring about some estimate of a temperature of dark matter. The idea is this. A black hole has a temperature given by T ~ A/4, for A = 4pi r^2 and r = 2M, the area of the black hole event horizon. Presumably black holes can absorb dark matter. After all the no hair theorem of black holes indicates they are determined by mass, charge and their angular momentum. So how a black hole acquires its mass is independent of the conditions or state of that matter. If a black hole absorbs a unit of mass then its mass changes as M —> M + &m and its temperature decreases by T —> T + 4pi M&m + O(&m^2). In order for this to make thermodynamic sense the dark matter must have a temperature larger than the black hole temperature.
I’ll have to look this up but I recall (as I am still drinking coffee to wake up) last year that some measurements of dark matter velocities (measured by some means) indicated a temperature for dark matter.
Another thought occurred to me, which is that dark matter might play a bigger role in galaxy formation by its dynamics in an expanding cosmology. Dark matter appears to be like cobwebs, or as a fluid a bit like goo. As the universe expands it is stretched into longer tendrils which connect up galaxies. As these are stretched if this “fluid” will the constrict these tendrils and “blobs” around galaxies. I think this should then tighten the region of space which binds luminous matter together.
Lawrence B. Crowell
Lawrence,
This description reminds me of plasma cosmology;
http://www.plasmacosmology.net/
[...] John Conway, a physicist at the University of California, has written a post called ‘What’s the (Dark) Matter?’ where someone has referred to my post here as my ‘belief’ that gravitons have a spin [...]
Of course dark matter can’t be plasma of charged particles. That would be luminous, and plasmas being a gas of charged particles is the epitome of luminous matter.
Lawrence B. Crowell
Dark Matter is a 2nd state of matter, or matter could be a 2nd state of dark matter.
It’s like what came first, matter or dark matter.
If strings are ever found, they would exist in a different state in dark matter. The question is want would cause these changes. Black holes, over expansion of matter, ect.. Think of the universe as if it was in a cycle.
The web between galaxies are trails. put some bubbles on a counter top and blow on it, as it travels across the surface it leaves a trail, expansion works the same way.
Tom
What else holds the cosmic web together if not dark matter? On the other hand, the persistent null results each time we progress further into the favored ‘parameter space’ should, by this point, be a major concern for CDM adherents. If DM only interacts gravitationally, then we will never be able to extinguish for empirically equivalent theories.
The dark matter tendrils might be analogous to cosmic strings. During the inflationary phase of the universe gauge fields and their sources may have entered into condensate states which defined a BPS mass M ~ QQ*, for Q and Q* the “charge” of a field and Q* its dual. This duality is given by an S-duality or Montonen-Olive duality between gauge electric-like and magnetic-like monopole charges. The Montonen-Olive duality is an interesting version of the Sommerfeld quantization condition
These condensates also have some properties dual to the interior of a black hole on a D-brane. The rapid exponential expansion of the universe then stretches these condensates into cosmic strings.
Some RHIC data suggests that quark-gluon plasmas have properties similar to this. Further, textures in the cosmic microwave background have a kertosis which indicates a possible Einstein lensing by a cosmic string.
The dark matter tendrils may well be dark matter analogues to cosmic strings. A tendril may during the current “eternal inflation,” the observed accelerated expansion of the universe, evolve into a form of cosmic string in the distant future. So we might posit there exists some symmetry, eg, supersymmetry or S-T-U duality or some new form of symmetry, between dark matter and regular matter as well as with the two inflationary phases of the universe — the early one which inflated the universe and broke the symmetry of gauge fields and the current one which is stretching dark matter tendrils into a possible new form of cosmic string. Oh, yeah — maybe we have to throw dark energy into the mix as well!
All of this profoundly challenges our basic understanding of physics and cosmology. Yet this is what makes science interesting. Questions are far more interesting then answers, and we are faced with some very big and serious questions about the foundations of physics and the universe.
Lawrence B. Crowell
I don’t know if it is simply coincidence or relative synchronicity, but just this past week i was preparing to write to Cosmic Variance and request an update on WIMPs, dark matter, and other aspects of theories. I had been rereading several books from the 1990s and had begun to wonder how the research had been going. And alas i get John’s thread and comments to fill me in. Huge and grateful appreciation for it all, thanks.
“A black hole might grow quite nicely and quietly in a region of dark matter. ”
So find a black hole/white dwarf* binary out in a dark, massive part of the galaxy, get radial velocity on the dwarf, and see if it increases with time**.
Bob’s your uncle.
* No stellar wind- simpler system
** As a geologist, I see nothing wrong with experiments that take millions of years to complete.
Lawrence that was great.
Within a lifetime you would not observe much change in a black hole mass. A region of dark matter has a mass-density only about 10-100 times that of the whole universe 10^{-29}gm/cm^3. So a black hole there would take a while to absorb a whole lot of dark matter. It just seems to me that the dark matter would not resist very much being gravitationally pulled into a black hole. A black hole would just sip it down over time and slowly grow, while luminous matter has a lot of frictional resistance. Ordinary matter falling in heats up, emits radiation, and that pushes matter away from the black hole.
So maybe light passing through regions of dark matter would microlens around black holes that are statistically more massive than regions free of dark matter. Obviously this is fraught with other issues concerning the distribution of black holes in a region removed from a galaxy, but a lot of work has been done on mass distributions with microlensing. To be honest I am no expert in this area.
Lawrence B. Crowell
In order to account for the observed galaxy dynamics,
It was natural to invent the extra mass that was needed
to explain the kinetics of the large scale. Since the extra
mass was never observed directly it was called dark matter.
The irony of the situation is that scientist’s started to
believe that there was such matter existing in real life.
In spite of having painstakingly developed the standard
model of real fermionic and bosonic matter, they were ready
to accept the existence of a third kind of matter i.e. dark matter,
in order to account for the unusual behavior of gravity, while all the time
having known that they could not unite gravity into the standard
particle model.
Some have therefore tried the next best obvious solution to the
problem and resorted to modify the behavior of gravity at large scales.
MOND and relativistic attempts of extending MOND are more
logical but fails.
I have pursued another alternative to all of the above. I announce that
the Newtonian law of gravity is universal, but the real observed mass of
objects are virtually multiplied at very long range from the object,
effectively mimicking the so called dark matter. I declare that the secret
of the mass multiplier is the existence of a cosmic size 4th bounded
spatial dimension. The 4th dimension also gave me a bonus, I can
now explain most of other problems in physics.
Folks, see my web site for a preview of things to come at:
cosmicdarkmatter.com
Tissa, see discussion starting 20 down. There are a lot of people in that boat. Don’t get trapped thinking you’re the “all seeing I.” Science isn’t for nabbing the Nobel all oneself, but for the progression of the discipline.
The notion of a possible reduction in mass over distance is interesting, where distantly observed mass is stretched or spread out with a decrease in ‘intensity’ much like the propagation of light. Perhaps if Lawrence reads these comments again he can give his two cents.
Wayne
Well this web site (cosmicdarkmatter.com) is a “I have a theory” sort of thing. For myself I have a whole lot more questions than theories. I also dislike the term “theory of everything.” A moment’s thought should indicate a theory that explains everything in fact might explain nothing.
A particle in an orbit with a constant mass-energy density of dark matter will orbit according to the dynamics
where R is the radius of a dark matter halo or ball in space containing dark matter. I am doing this off the top of my head, but I think this is right “modulo” maybe a 4-pi. But the crucial thing is that the equation of motion is that of a mass on a spring or harmonic oscillator. So all particles in the dark matter halo will orbit with the same frequency of rotation. This is why our galaxy rotates a bit like a wheel, instead of there being a Kepler law motion that would wind up the arms of the galaxy.
There are a few little issues about this, but for our astro-phys 101 discussion this is good enough.
I suspect this website comes down to the adage “A little knowledge is … ” Dark matter should exist in some grand system of gauge fields and gravitation. This presumably requires physics which appeals to the heterotic group E_8, or in string theory the complexified CE_8 = E_8xE_8, which is a model of the heterotic string.
In the ADE classification of standard groups E_8 is the largest real group. It might sound strange, but you run out of group theory beyond this level. Except if you go to sporadic groups, which are modular systems often composed of ADE groups. The E_8 is the largest classical group which is defined in the 256 elements of N = 8 supersymmetry or a graded algebraic system which satisfies the Coleman-Mandula theorem. The C-M theorem tells us that physics can only involve a system of external symmetries (relativity) a system of internal symmetries (gauge theory) and the CPT discrete symmetry.
There is a bit of a debate on energy conservation in general relativity or cosmology. I can illuminate this more later. The E_8 breaks down into subgroups with spin(6) = SO(8) ~ SO(4)xSO(4). One of these involves the Pati-Salam weak interaction model and the other relativity. Yet with relativity the gauge group is SO(3,1), which is hyperbolic. Hyperbolic groups are a bit strange, for they are non-compact. A sequence of group generators will not converge in a Cauchy sequence. The hyperbolic asymptotic behavior insures that some sequences will head off “to infinity” with no finite convergence. So there is a whole set of problems with equating holonomies, loop space variables etc, with the group theory of curvatures. One consequence of this is that the Noether theorem does not apply in the same way, except on tensors — such as D_aT^{ab} = 0 continuity condition on the momentum-energy tensor.
There are 26 sporadic groups from the Mathieu groups leading up to something called the Fischer-Griess group (the Monster group). The primary focus of mine is with the Mathieu group M24 with 196560 elements in 24 dimensions on a 24-dimensional lattice, with roots for 3 “copies” of the E_8. The elements of the M24 define a normalizer of the Monster, which along with the Conway group Co1 are richly involved with the structure of the Monster, with about 8.8×10^{50} elements. There is an actual integer number for this based on the prime composition of the group, but that gets a bit “heady.” Beyond the monster group, or some Borcherds extensions into so called “moonshine” or monsterous moonshine, you again run out of group theory. If there exists symmetry beyond this level of sporadic groups it involves mathematics unknown to us.
So dark matter might presumably be lurking in this. Don’t ask me where, for I am asking the same question — I have more questions than theories.
Lawrence B. Crowell
Correction. There should be no 1/R^3 in the formula for gravity
L. C.
/nod
Well, Lawrence, I’m very glad you are one of the guys working on the
because honestly, we as humankind wouldn’t get that far without minds like yours working in realms like that. Cheers to you.
I followed as long as I could, but sir, as Sam Cox said, we are in your classroom. Thanks for hanging out with us. I’d add something more constructive if I could.
Wayne
[...] I just discovered -better late than never- that my friend John wrote about the same result at Cosmic [...]
Thanks Wayne, looks like I got a lot more than two cents worth
from Lawrence. I believe in Keep It Plain & Simple(KIPS). What
I have found is that the universe can be modeled using simple
mechanical geometric arguments, if and only if, we are prepared to
accept the additional existence of a large cosmic size(a few Kpc)
bounded 4th spatial dimension. By the way, all I am trying to do
is if I can convince some of the professionals to investigate my
hypothesis on dark matter before dismissing it off hand. My feeling
is one day, dark matter is taking the course of what happened to the
fictitious Luminiferous Aether , after a lot of wasted effort.
As for the Nobel, forget about it, the chances are as good as
winning the lottery.
/Tissa
I didn’t mean that as too hard a stab, there was just a tad feeling of “mine” syndrome from the previous post. I completely agree with you on the nature of DM being something that can in further discovery be ruled out unanimously as the ever-recurring Aether. Whenever some data set appears in experiments that defies conventional thinking, generally all cases that attempt to use conventional criteria in understanding such phenomena will discover a new “Aether object” or a concept equally as mysterious and vague.
It is only when a new perspective, a novel approach is taken on the phenomena that we truly understand its, as you put it, plainness and simplicity. The pattern recurs from Galileo to Newton to Maxwell to Einstein, and finally the modern Schroedinger brainchild QM. Approximately every 100 or so years humanity has taken a leap of awareness in the perspective of empirical science. We are due for a new perspective, and I firmly believe this lie in the extension of our as yet primordial grasp of 4 dimensions to additional dimensions to accurately conceptualize the cosmos. Whatever leaps of consciousness are required, they will be taken to solve such conundrums, and I have no doubt in the tenacity and success of our modern (and developing) physicists to do so.
Wayne
Great post, John. I have been very interested in the CDMS and noble gas dark matter searches. I have often wondered, as apparently you have, if dark matter interacts weakly. Do we have any evidence to suggest that it does, or are we just hoping that it might?
Brian
Where did I read that dark energy and dark matter might just be (due to) a scalar field. And, does scalar field have anything to do with scale?
There are some theories by Moffat and others which have scalars in gravitation. I am a bit agnostic about these things, but these theories give so called MOND gravitational theories which supposedly account for dark matter.
Lawrence B. Crowell
New research headed by Sebastien Peirani (at the Institut d’Astrophysique de Paris, France) suggests only a very small fraction of a SMBH is composed from dark matter as it evolved. Dark matter is predicted to be collisionless and will be scattered very easily by baryonic gas clouds and stars. It seems unlikely that dark matter will be able to stay inside the black hole’s accretion disk for very long before it is repelled by all the “normal” matter being pulled toward the event horizon.
By modelling a “typical” accretion disk and comparing the results with observations of quasar luminosity, the French group found that most of the matter fuelling the SMBHs is relativistic baryonic matter. At a critical distance, outside the black hole, baryonic matter from the accretion disk is accelerated to a significant fraction of the speed of light, emitting radiation. Comparing this with simulations of a collisionless disk (i.e. the characteristics of dark matter), the baryonic model fits observations the best.
http://www.universetoday.com/2008/03/08/greedy-supermassive-black-holes-dislike-dark-matter/
I am convinced that dark matter and dark energy are part and parcel of the same cosmic entity. This assumption is at its heart, rooted in the equivalence of matter and energy and the great proportion itself.
I have (on the NASA website) been reading the recent papers on the WMAP results and note that dark energy was (as measured by the WMAP equipment) a negligable percentage of the universal mass in the earliest epochs but that the percentage of same has been increasing progressively (to presently better than 70%) as the universe has developed.
This increase is very likely the result of the increasing percentage of the universes matter progressively relegated to the singular condition…the Planck Realm as a whole and related (entangled) multitudes of Black Holes…huge energy compactions- as observed and measured from our location in scale (coordinates/frame of reference).
I cannot conceptually grasp why some scientists persist in a search for extra large dimensions in what is by definition, a 4 dimensional hierarchy. If other dimensions exist, as is almost certain, they are just as “large” as the 4 with which we are familiar…only over the horizon…detectable most reasonably (and most likely) ONLY by their mass….and there is no shortage of “missing mass” in the universe!
So….gravity is not scale invariant, yet photons are. When we look out in space we are seeing these two things. Whatever effect scale has, we might see it.
Whenever someone says scale invariance it makes me smile. The un-particle idea is fantastic stuff, I think the intuitive leap it takes to define a potentially significant effect in the cosmos based on scale invariance (in contrast to the scale variance of particulate matter) seems to add a missing piece that I think may show up as gravity en masse, instead of say, the graviton. Does anyone know what evidence says gravity cannot be scale invariant?
Here’s an article on it. I think someone had mentioned it earlier, I think its good to have a source here too.
http://www.physorg.com/news100753984.html
Sam, I had a query about eternally fixed coordinate system of the 7 Dimensional, I didn’t want to fill up space here, but the email contact you have on your site doesn’t work. Just curious if you might have another contact to ask a couple clarification questions.
Wayne
Sandy,
Appreciated your comments- and your intuitive sense! Photons seem to be close to scale invariant, from our frame of reference anyway. Photons not only can be measured as wavelike or particulate…they vary in mass from the negligible- as Schwarzschild asserted 0+ mass- to a universe filling entangled matrix. Yet, as you point out, they have a certain, but not perfect scale invariant quality about them…think of the “constant” speed of light!
Remember however that photons ARE affected by gravity…albeit slightly, and that ultimately, they- as a form of matter/energy are very subject to gravity near Black holes. In fact, the way photons behave near the 4D event horizon “particulate” surfaces near the Planck Realm relates to the way the universe is observed by us…gravitational red shift and time dilation, for examples.
Gravity, almost by definition, is related to energy density variation and is obviously affected by same- and scale. In fact, scale, dimensions and the like result from the relationships between singularity based energy densities which we as observers measure (partly) by assigning the property of “gravity”…the inverse square with distance law etc.
There is not enough space here to get into the mechanism by which we cross-read the universe…holigraphy…but the process by which (from a 4D frame) a black hole with an event horizon radius about the size of the solar system is able to contain all the information in the universe is a matter of very advanced cosmological study (I resist the temptation to use the word “speculation” because we know with reasonable certainty the “information paradox” does NOT exist and that all information in the universe (including what “evaporates” as Hawking radiation), is eternally conserved in the hierarchy.
Interesting thoughts…
Wayne,
The concept on my site is archived material and I have updated only the description on the home page from time to time. Sean has my Email address, and I don’t mind giving it to you. I would be interested in your thoughts! The address is samacox@comcast.net
Best wishes…a very interesting thread! Sam Cox
It makes sense to me that some aspect of gravity, possibly having to do with scale, will eventually be replacing dark energy and dark matter. We really haven’t fully cracked gravity yet, have we?
http://physicsworld.com/cws/article/print/24991
http://pda.physorg.com/lofi-news-dark-matter-energy_120998817.html
Also (at the risk of gross oversimplification) if dark energy is primarily used to explain why the expansion of the universe is (or appears to be) accelerating, and if dark matter is used to explain why parts (or the whole) stay together, why not assume they are the same, subtract one from the other, and use that number as the “missing” force/matter that we are looking for in the universe? And….if we are dealing with something that acts both particle-like and non-particle-like, does that narrow things down a bit?
Wayne
A Dark Matter thought experiment.
1) Dark Matter was invented to augment the observed motion of
real visible matter, right? right!
2) Dark Matter interacts with real matter via gravitational forces
only, right? right!
3) Dark Matter too interacts with Dark Matter gravitationally
right? right!
4) Therefore Dark Matter must take part in the orbital dynamics
of the system, right? right!
5) The only difference is that Dark Matter cannot be seen, other
wise, it takes part in the gravitational dynamics of the system,
which is purely Newtonian motion, right? right!
Now that we agree, let us do a pure thought experiment.
Let us do an N-Body simulation, where N will be in the billions.
6) All N Bodies will therefore do a Newtonian Samba. Each of the
N Bodies will clearly have rotational motion velocities defined
by Newton’s laws. Therefore only Newton’s Law accounts for
their motions.
7) Now we will use some magic, we will make 90% of the N bodies
invisible, and call them Dark Matter!
8).What do you think would happen to the 10% that are still visible?
9).You guessed! they will keep moving as before and still obey
Newtonian Law’s with no velocity discrepancies.
10)Moral of the story is, Dark Matter don’t matter.
11)There must be another way like I said before!
/Tissa Perera
I wrote this on physics list (no a blog) and it involves cosmology and consciousness. I present a sort of conjecture which is interesting, though some of the more metaphysical things I say here I offer as possibilities and not as anything serious. I fugured this might be interesting.
——————
We have to admit that science explains everything which is measurable. Does science explain everything? I am non-committal on this question, and to be honest I can’t answer this in the affirmative with a strong sense. Consciousness, or what some call the hard problem or qualia or … , might simply be outside the perview of science to address. Also Hawking’s question on what makes the equations “fly” might also not be scientifically answerable.
So suppose you have this holographic universe, and I have written on this with respect to the duality between AdS and conformal field theory and the path integral of the universe, then this is a path integral that takes one form of nothing and maps it into another form of nothing. As a digression this is how a set of non-equivalent vacua are one nothing, and where the symmetries on one vacua define particle states on another, which means there is no global symmetry to the universe. This means there are only local symmetries that act on a vacuum, but these symmetries do not act on a Lagrangian or path integral determined by a cosmological action. Bruce and I talked a bit about this with energy conservation in cosmology. So, okay we have one “nothing,” and the other nothing is the attractor point for the cosmology. This is a Minkowski space and a perfect void = conformal infinity of the AdS. So all of this stuff going on in the universe, collapsing black holes, mitosis of cells, Spitzer having fun with call girls and …, are just a way of mapping conformal group structure around locally so as to connect these two nothings.
Ok, now we are in this hologram! We are caught in this holographic map. We have consciousness and we percieve things, feel things and make judgements about things, such as “That train exists and I’d better not cross the tracks in front of it.” So we assign this abstract category called ontology to things, or we make these holographic phase interferences into “thingy” things which we assign ontology to. So maybe, and I am not committed to this idea and only find it interesting, this holographic map is assigned an ontology because it gives rise to conscious entities within it that observe it, or if nothing else stub their toe on that stone and yell ouch! Further, we assign ontology to the early universe by collecting light it emits in the distant past and form images and other forms of information, and I use the present tense “emits” because light is timeless or null and this process has a timeless element to it.
Does this have any connection to physics? Maybe at best weakly, for as I mentioned at the Planck scale I suspect states exist in self-referential loops of entanglements with no “structure.” On a scale larger than the Planck scale what is called physical structure or symmetry is something which proximally emerges as some accident because consciousness can observe it. Think of symmetry emergent by a chaotic process similar to a MonteCarlo simulation of possible outcomes and optimizing for structures which can exist on a larger scale. On the other hand consciousness may also be a matter of Godelian loops (and whether quantum or classical is not relevant), Hofstaedter seems to think so, which is a part of “closing the loop.” Also the universe with a cosmological constant is one which, as we argued a couple of weeks ago, has no time Killing vector and thus there is energy conservation law. If my inequivalent vacua theory is correct then it means the universe admits no global symmetry, including the Coleman-Mandula theorem on the maximal permissible set of symmetries for the S-matrix. So this “loops” again from the Planck scale to the cosmological scale, where after all the universe is a chaotically inflated region near the Planck scale and problably ultimately from the Planck scale.
This is likely where physics connects with meta-physics. If physics reaches this point, ideally if we have some physical theory of quantum gravity & cosmology with observational and experimental evidence, then this would be the beginning of where foundational physics might begin to end. As this continues we might find that physics ends off at the same stage it left off from, called philosophy. I think we are a ways from an end of physics, but we might be seeing the light and the end of the tunnel (or what some might say is a darkness at the end of the light) before terribly long. It is an optomistic/pessimistic thing, for it means that there is some end result to this and it is not just an endless game, but on the other hand it might mean a sort of dismal future awaits future generations. Physics may become a sort of service field to molecular biology and applied fields this century. But all things must end, and frankly I suspect our tenure on this planet will be ending pretty shortly — at least on a geological time scale. So maybe we will at accomplish this, which might elevate our existence here some epsilon distance above absurdity. Then again it might just all be howling at the moon.
So am I committed to this idea of consciousness and ontology in the universe? It is an interesting idea. It suggests that these hard things which we call particles are considered as ontologically real because, well we consciously determine them to be.
Lawrence B. Crowell
Dark matter and dark energy are the gap between theory and observation.
What if the age of the universe is much older, say infinitely. Would an infinite timeframe overcome the drag of galactic evolution, so that the outer rings are pulled along at the same speed as the inner rings?
If space expands, but the universe doesn’t, since gravity is collapsing space at similar rates to which it is expanding, wouldn’t this create additional pressure on these gravitational systems and this explain some of the dark matter effects?
Lawrence,
Units of time always go from beginning to end, but the process of time is constantly going on to new beginnings.
Think of left brained structure as the units/nouns, the narrative structure from beginning to end, birth to death, Genesis to Armageddon, Big Bang to fadeout, prologue to postscript, dawn to dusk.
Meanwhile the process, the verb, is constantly going on to the next generation, the new day. These clear points in time have no consistancy, other then that of frames of a film, going from being in the future to being in the past, aspercveption, energy, life, etc. goes on to the next frame, past to future…
The universe consists of expanding energy and collapsing mass. Mass is the unit/structure, going from start to finish, initiation to consumption, birth to death. The energy is constantly radiating away from old collapsing structure to join with and grow new structure. Yes, all the details don’t always perfectly connect, but that doesn’t mean these missing links didn’t exist, only that the information of them is lost.
So the basic pattern is of a cycle of expansion, contraction. Two directions of time, as physical reality goes from past events to future ones, while these events go from future potential to past circumstance.
The real illusion is that the structure appears to be the reality, when it is just passing impermanent information. Consciousness, like the energy, goes to the future, even though what it is conscious of goes into the past.
LC,
“So am I committed to this idea of consciousness and ontology in the universe? It is an interesting idea. It suggests that these hard things which we call particles are considered as ontologically real because, well we consciously determine them to be.”
I think physics strongly implies that information and complexity are real, that they are conserved, and probably slowly built upon. Yes there is a connection between observation and existence. In fact the way we observe determines the reality each of us measure and must contend with in our daily lives.
However, is there such a thing as non-existence (and therefore non-observation)at all? I doubt it. Not only is the universe continuously observed and therefore eternally existing…WE are continuously existing. From separate coordinates and in an infinite variety of ways the universe is eternally being observed and is therefore fully and continuously (eternally) existing.
I laugh when someone says that they look forward to the “rest” of death. There is no passage of time in death. At death we instantly become re-aware of existence. Nobody attends his or her own funeral- only those of other folks! Only the quality of our consciousness changes as we pass “death” and once again begin the process of “life” and the re-experience of the process of our individual identity.
The same thing applies to the antelope taken by the lion or the fish eaten by a shark, the tree in our yard…to all living. We are permanent, embedded and conserved information at a certain “place” in space and time…specific coordinates…and with that location and information, have unique perspective and point of view.
When we try to grab anything in the universe, we find it attached to everything else…dependent on everything else. Good ecology and good GR too.
Sam,
We tend to equate awareness with intellect, whether it’s the all-knowing ideal of theism, or the emergent consciousnesss of atheism, but it it would seem that knowledge is structural organization that grows in complexity, until its supporting organism breaks down and dies, leaving intellectual achievement and biological remnant as foundation and fertilizer for succeeding generations of life. So this structure starts as future potential and passes into past circumstance. Meanwhile the element of awareness passes onto the next generation, which has had the mental reset button pushed by death of older generations. To the extent we are this raw physical existance, proceeding through the generations, it would seem we are all part of one larger awareness/organism that is recycling its cells. So to the extent we continue beyond our own death, it is through those to whom we have passed our knowledge and emotional strength. We are like sentences in a larger story, in that our purpose is how well we communicate and expand on what came before to what comes after. Our end is just punctuation, not destination.
This all warms my spirit. I couldn’t have said it better than Lawrence, Sam, or John. Well put everyone. Indeed it seemed like each of you were providing a different solution to respond to each other, but truly, you all said the exact same things. It is the fact that each of us feel so strongly that there is this idea, this one notion that we as humanity have this compulsion towards, this drawing into a higher form that everyone wants to share their understanding of that compulsion, to show that they are each thinking alike. That this feeling is shared, and communal, and indeed inseparable.
It has taken a long time in the experience of life on Earth, and humanity as a brief spectacle upon in, where we as the cells or sentences or pieces or wholes have come to realize the form that has arisen, and indeed has always been present, from the inclusion of each member, each individual. We are sentences reading our own story, cells witnessing the beauty of a sunrise, pieces feeling the structure of wholeness.
The most indomitable strength